Third harmonic generation of a relativistic self-focusing laser in plasma under exponential density ramp

Present study focuses on self-focusing and its effect on third harmonic generation (THG) of a Gaussian laser beam in plasma under the influence of exponential density ramp. Relativistic nonlinearity has been taken into account which is aroused due the modification of electron’s mass in the presence of high intensity laser. Under strong ponderomotive force, electrons acquire very high quiver velocity and mass variation takes place. Equations for beam width parameter of incident laser and the amplitude of THG have been derived under WKB and paraxial ray approximation, and solved them numerically. It is found that the presence of exponential plasma density ramp results strong self-focusing of laser which further leads to enhance the efficiency of THG. Wiggler magnetic field adds an additional momentum to the photons of third harmonic due to which appreciable gain is observed in the normalized amplitude of THG. Significant enhancement in the THG amplitude has been reported in the presence of exponential density ramp for optimum values of intensity of incident laser, wiggler magnetic field and plasma frequency.

Second Harmonic Generation Induced by Surface Plasma Wave on Metallic Surface in the Presence of Wiggler Magnetic Field

Under the influence of wiggler magnetic field, the phenomenon of second harmonic generation at the metal-semiconductor interface, induced by surface plasma wave (SPW) has been investigated. Metals like Cu, Ag and Al, each with a thin layer of n-InSb over it, are considered for our study. Laser light is incident on metal layered on glass prism in attenuated total reflection Kretschmann configuration (ATR) which generates SPW. The SPW further interacts nonlinearly with the electrons of n-type semiconductor layered over the metal, leading to second harmonic generation (SHG). The presence of an external wiggler magnetic field makes the process resonant and helps in phase matching. Relatively more enhancement in the amplitude of the second harmonic is observed for Cu-InSb as compared to Ag-InSb and Al-InSb. Numerical analysis shows that the enhancement in the amplitude of SHG increases with the wiggler magnetic field.

Electron acceleration of a surface wave propagating in wiggler-assisted plasma

In this paper, we study the electron acceleration by a surface plasma wave (SPW) propagating through two parallel metal sheets in the presence of wiggler magnetic field strength. The configuration of interest consists of a helical magnetostatic wiggler, an external magnetic field and two parallel metal half-spaces. Dispersion relation of SPW in the attendance of helical magnetostatic wiggler is recognized and observed as compared with that of without wiggler field. A numerical calculation in Matlab software was developed by employing the fourth-order Runge–Kutta method for studying the electron energy and electron trajectory in SPW. Numerical results depict that with increasing of [Formula: see text]-parameter [Formula: see text] is the ratio of wiggler frequency to plasma frequency), minimum modes of SPW have an increasing trend and with increase of the wiggler frequency, the normalized frequencies decreased and a gap appeared between them. Furthermore, it is seen that with increase of the [Formula: see text]-parameter, the value of the kinetic energy as compared with the absence of the wiggler magnetic field increased. In fact, the electron energy gained is higher in the presence of a helical magnetostatic wiggler as compared with the absence of wiggler field. In addition, it is observed that due to effects of the wiggler field and SPW field, the electron traverses more distance in the propagation direction of the laser pulse.

Exponential density transition-based enhanced second harmonic generation in plasma

Enhanced harmonic generation of second order based on exponential density ramp in plasma has been noticed. It is well known that self-focusing of pump laser induces a transverse intensity gradient, which gives rise to the plasma wave at the pump frequency. Highly intense Gaussian laser with exponential density ramp profile generates a second harmonic pulse in plasma. It is noticed that the amplitude of second-harmonic pulse varies periodically with the distance and reaches its peak value in the focal region. Further, it is found that exponential plasma density ramp is useful for stronger self-focusing, which lead to rise second harmonic generation (SHG). Wiggler magnetic field provides the additional angular momentum required for second harmonic photon and aids in growing of resonant process. One may clearly see that exponential plasma density ramp imparts a major role in enhancing the SHG in plasma. Further, the combined effect of exponential density ramp and wiggler magnetic field boosts the SHG in plasma.